Engine heat exchangers, such as charge air coolers and other coolers, may function to cool the temperature of charge air entering the intake manifold, providing charge air with higher density and thus increased engine power and improved fuel efficiency. Further, cooled charge air may lower combustion temperatures and aid in controlling certain engine emissions. However, under certain conditions, such as when the air in the heat exchanger is cooled below its dew point, condensate can form within the heat exchanger. The condensate may accumulate and then be swept to the engine, causing misfire and other problems; it can also reduce the effectiveness of the heat exchanger over time. Further, particularly in exhaust gas recirculation coolers which cool exhaust being recirculated back to the intake, acidic compounds may be present in the condensate, resulting in degradation to the cooler and/or downstream components.
To prevent the accumulation of condensate within the heat exchanger, a bypass line may be provided around the heat exchanger. During conditions in which condensate is predicted to form in the cooler, the air normally provided to the heat exchanger may be routed through the bypass line to avoid possible deposition of condensate within the heat exchanger. However, such bypass lines may be expensive and increase the complexity of the engine control system strategy. Further, it may be difficult to accurately predict when condensation may form, resulting in unnecessary bypass of the air and increased temperature and decreased density of the charge air.
The inventors have recognized the issues with the above approach and offer a method to at least partly address them. In one embodiment, a method for an engine comprises increasing exhaust gas recirculation (EGR) flow responsive to condensation in an EGR cooler.
In this way, the flow of EGR may be increased in response to condensation in an EGR cooler. In one example, the EGR flow may be increased when an estimated amount of accumulated condensate in the EGR cooler exceeds a threshold. The amount of accumulated condensate in the EGR cooler may be estimated based on both an amount of condensation that forms within the EGR cooler, as well as an amount of condensate that evaporates out of the EGR cooler over a given duration. By tracking both the amount of formed condensate as well as the amount of evaporated condensate, the amount of condensate that actually accumulates in the heat exchanger may be more accurately determined. Further, by adjusting EGR flow responsive to condensation in the cooler, condensate may be removed without utilizing a complicated bypass system, or in addition to such a bypass system.
The above advantages and other advantages, and features of the present description will be readily apparent from the following Detailed Description when taken alone or in connection with the accompanying drawings.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.